Select Defoamers/ Anti-Foaming Agents for Adhesives

Defoamers/ Anti-foaming Agents are primarily used in formulating waterborne adhesives, but they are also used in solvent-borne and solvent-free systems. Selection of right defoaming agent mainly depends on the distinct adhesive formulation, processes employed in formulation or conversion. Know more about various factors, in detail, while selecting and using
anti-foaming agents depending on your formulation. You can get a review of the problems caused by foam formation, the mechanism and factors that cause foaming, and the chemical agents that can be used to hinder or eliminate the formation of foam in adhesive systems.

Problems Encountered Due to Foaming

Select Defoamers for Adhesive Formulations Foaming is a problem that plagues many adhesive applications. Emulsion adhesives are especially prone to the troubles and expensive consequences created by foaming.

When any emulsion is moving in contact with air, there is a risk of foam formation.

Therefore, foam is generally encountered when mixing the adhesive or during high speed coating processes.

Foam is often an undesirable consequence of the waterborne adhesive polymerization, compounding, or conversion processes. Foam can also develop during other stages of the adhesive’s life cycle such as during filling or packaging, transportation, and coating or application.

Foaming can deteriorate adhesive system by:

  • Reducing Adhesion and Aesthetics: Foaming can lead to:

    • Process inefficiency
    • Overflow in tanks
    • Instability of the adhesive emulsion, and
    • Poor substrate coating

    In applying an adhesive coating, for example, foaming problems can result in several types of defects, most notably:

    • Cratering
    • Pin-holing (fisheyes), and
    • Dewetting

    These not only reduce the aesthetics of the adhesive coating, but also can significantly reduce the adhesion properties of the finished product.

  • Increasing Viscosity of the System: The formation of bubbles or foam on a thin adhesive coating requires special consideration. In a waterborne adhesive coating applied to a substrate, as the water in the formulation evaporates at the surface it causes an increase in viscosity.

    This viscosity increase prevents the smaller bubbles within the coating from rising to the surface, and also inhibits the possibility of the liquid from flowing back into the space originally occupied by the bubble. This situation causes craters to form in the coating. The smaller bubbles that remain in the coating because pinholes as the film thickness shrinks, making the bubbles create a void between the substrate and the air interface.

So, what could be the possible solution for these problems?

And Here Comes the Role of Defoamers...


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